Common sportswear such as sneakers, protective pads, helmets, etc, have used traditional sponge, foam rubber, or polymer compositions as shock-absorbing materials. Air inflated cushions have gradually been taking the place of these traditional materials, utilizing gas or liquid contained in an air cushion for absorbing shocks.
An air cushion is generally made of two sheets placed one on the other and sealed tightly at outer circumferential edges to form a hollow interior inflated with a gas or a liquid. Another kind of air cushion is made by means of an injection molding process to produce a three dimensional air cushion with a hollow interior and then inflating air chambers provided therein with a gas or a liquid.
A cushion as shown in FIG. 1 is made of two sheets placed one on the other and fused together to have an upper flat surface. When a shock is imparted to its surface, it is received on a spot of the cushion and then dispersed gradually to other surfaces. This kind of cushion absorbs only a little shock, and therefore required for energy dispersion is comparatively large. In addition, its center of gravity is high so that instability produced by shock is accordingly increased.
As can be understood from the stabilizing principles of physics, a cushion with a flat surface can barely support an exterior high force. Such a cushion can only have a shock-absorbing function for an object the cushion is protecting
A hollow three dimensional cushion as shown in FIG. 2, made by means of an injection molding process, may have a curved upper surface for contacting an object protected by it, but the cushion does not have a structure of shape memorization, and has to rely on an exterior layer added on its surface to form its upper curved surface. The whole curved surface of the cushion is nearly under the lower surface of the object protected, i.e. a shocking surface so that when a shock or a pressure is added to the surface of the cushion by the object, the shock or pressure force cannot be dispersed to two sides, as the cushion is provided with no higher side walls than the height of the cushion. Therefore a shock energy it receives is only temporarily converted into a side effect, limited in absorbing and stabilizing shock, which is not an ideal structure for a cushion.
The main purpose of the invention is to offer an air cushion with a better structure for shock-absorbing and stability.
A three dimensional air cushion according to the invention is shown in FIG. 3, intended to have the following advantages.
1. Comparatively higher sides, two or three of which are provided with air chambers extending from a center portion so that the air cushion and an object it protects may contact with a curved surface so that dispersion of a surface receiving shock may be increased to minimize moving shock energy, and to maximize a compressible area, and consequently to obtain the largest shock-absorbing effect.
2. It can sufficiently convert shock energy added on an intermediate upper surface into outer side support energy.
3. When shock or pressure disappears, the side support energy can completely return to the point of the shock, forming a rebound energy producing an excellent rebounding effect.
The buffer-functioning and shock-absorbing effect of air cushions according to the invention has been tested by SATRA FOOTWEAR TECHNOLOGY CENTER in England, and proved to be so far the best structural design for practical use.